unlockDialog: Use GdmUtil.AuthPrompt instead of ModalDialog
commit ea02380c1524c28e6538ffedb789a12c298742ab made the login
screen stop using ModalDialog. It makes sense for the unlock
code to also stop using ModalDialog, too (for similar reasons).
Now that the login screen's auth prompt code has been separated
out, the unlock dialog can use it to get the buttons and spinners
etc, that it was previously getting from ModalDialog.
This commit drops the ModalDialog usage in the unlock dialog, and
makes the unlock dialog use GdmUtil.AuthPrompt instead.
If the screenshield is up and the user starts typing, we need to
keep track of it and replay it later, otherwise what they type
will be ignored.
This is useful when the user has disable-user-list set to TRUE,
and will also be useful to bring feature parity between the
login screen and unlock screen.
theme: fix spacing for "Log in as another user" button
At some point the Not Listed? button was moved to align it better
in the login screen. That nudging made the "Log in as another user"
button (which uses the same style class) align worse.
This commit removes the padding at the unlock screen.